Edge protector for roof drill bit cutting insert

ABSTRACT

A rotary drill bit includes an elongate drill bit body having a slot at a forward end, an edge protector received in the slot of the drill bit body and a cutting insert having a cutting edge. The edge protector includes: a first side having a first bottom edge and a first top edge; a second side opposed to the first side, the second side having a second bottom edge and a second top edge; and a bottom portion adjoining the first bottom edge of the first side and the second bottom edge of the second side. The cutting insert is received in the edge protector such that the cutting edge is recessed below one of the first top edge of the first side or the second top edge of the second side.

BACKGROUND

The invention pertains generally to an excavating tool such as, forexample, a rotary drill bit useful for drilling through various earthstrata. More specifically, the invention pertains to a rotary drill bitwith a cutting insert such as, for example, a roof drill bit useful fordrilling bore holes in an underground mine.

The expansion of an underground mine, such as for example, a coal mine,requires digging a tunnel. Initially, this tunnel has an unsupportedroof. In order to support and stabilize the roof in an undergroundtunnel, bore holes are drilled in the roof, i.e., earth strata. Theapparatus used to drill these holes typically comprises a drill with along shaft, i.e., drill steel, attached to the drill. A roof drill bitis detachably mounted to the drill steel at the distal end thereof. Incertain roof drill bits, a hard cutting insert is mounted on a body ofthe roof drill bit.

A hard cutting insert for use in a roof drill bit is typically formed ofcemented tungsten carbide and can be secured by brazing the insertwithin a slot formed within a top working surface of the body of theroof drill bit. Tungsten carbide is a costly material and cuttinginserts are expensive to manufacture. Thus, it is important that thehard cutting insert be securely held in the slot of the roof drill bitso as not to become dislodged during use. Therefore, it is important touse a technique to produce an effective braze joint between the bit bodyand the hard cutting insert so as to provide a more durable tool havingan increased useful life.

Because tungsten carbide is a costly material and cutting inserts areexpensive to manufacture, it is also important that care be taken not todamage the hard cutting insert prior to being used, e.g. duringshipping, while installing the hard cutting insert, and/or prior to theoperation of the roof drill bit containing the hard cutting insert.Heretofore, hard cutting inserts have been damaged in one or more ofthese situations resulting in the hard cutting insert being defectiveand not suitable for use or having a shortened useful cutting life.

There is a need for improved roof drilling bits that overcomedisadvantages, limitations and shortcomings of known roof drilling bits.It would also be desirable to provide an improved roof drill bit thathas a longer useful life. It would also be desirable to provide a hardcutting insert that is not damaged prior to being used for a cuttingoperation.

SUMMARY

An aspect of the present invention is to provide rotary drill bit forengaging an earth strata material that includes an elongate drill bitbody having an axial forward end and an axial rearward end, wherein thedrill bit body contains a slot at the forward end. The rotary drill bitalso includes an edge protector received in the slot of the drill bitbody, the edge protector including: a first side having a first bottomedge and a first top edge; a second side opposed to the first side, thesecond side having a second bottom edge and a second top edge; and abottom portion adjoining the first bottom edge of the first side and thesecond bottom edge of the second side. The rotary drill bit alsoincludes a cutting insert having an elongate insert body rotatable abouta central axis, the elongate insert body having a pair of symmetricalhalves symmetrical about the central axis, each symmetrical halfincluding: a leading face; a top surface; and a cutting edge formedbetween the leading face and the top surface. The cutting insert isreceived in the edge protector such that the cutting edge is recessedbelow one of the first top edge of the first side or the second top edgeof the second side.

Another aspect of the present invention is to provide an edge protectorassembly for a rotary drill bit includes a shim having a first sidehaving a first bottom edge and a first top edge, a second side having asecond bottom edge and a second top edge, and a bottom portion adjoiningthe first bottom edge of the first side and the second bottom edge ofthe second side. The edge protector assembly also includes a cuttinginsert having a leading face, a top surface, and a cutting edge formedbetween the leading face and the top surface. The cutting insert isreceived in the shim such that the cutting edge is recessed below one ofthe first top edge of the first side or the second top edge of thesecond side.

A further aspect of the present invention is to provide an edgeprotector for a roof drill bit cutting insert having at least onecutting edge, the edge protector including a first side having a firstbottom edge and a first top edge, a second side having a second bottomedge and a second top edge, and a bottom portion adjoining the firstbottom edge of the first side and the second bottom edge of the secondside. The first side, the second side and the bottom portion areconfigured for receiving the cutting insert such that the at least onecutting edge is recessed below the first top edge of the first side orrecessed below the second top edge of the second side.

These and various other features and advantages will be apparent from areading of the following detailed description.

DRAWINGS

FIG. 1 is an exploded assembly view of a rotary drill bit, e.g. a roofdrill bit, in accordance with an aspect of the invention.

FIG. 2 is an isometric view of an edge protector shown in FIG. 1, inaccordance with an aspect of the invention.

FIG. 3 is a front elevational view of the edge protector shown in FIGS.1 and 2, in accordance with an aspect of the invention.

FIG. 4 is a front elevational view of the edge protector and cuttinginsert shown in FIG. 1 as assembled, in accordance with an aspect of theinvention.

FIG. 5 is an isometric view of one end of the assembled edge protectorand cutting insert shown in FIG. 4, in accordance with an aspect of theinvention.

FIG. 6 is an isometric view of another end of the assembled edgeprotector and cutting insert shown in FIG. 4, in accordance with anaspect of the invention

DETAILED DESCRIPTION

The following description is for purposes of illustrating variousaspects of the invention only and not for purposes of limiting the scopeof the invention.

Referring to the drawings, FIGS. 1-6 illustrates a rotary drill bitassembly in the form of a roof drill bit, generally designated as 10,useful for drilling through various earth strata, in accordance withvarious aspects of the invention. Roof drill bit assembly 10 has anelongate drill bit body 12 typically made of, for example, steel. Drillbit body 12 presents a generally cylindrical geometry. Drill bit body 12has an axial forward end 14 and an axial rearward end 16. Drill bit body12 contains a transverse slot 18 in the axial forward end thereof 14.Drill bit body 12 also may include a debris evacuation or collectionport 20 that is mediate between the axial forward end 14 and the axialrearward end 16. During the drilling operation, dirt and debris may passthrough the port 20.

The roof drill bit assembly 10 also includes a cutting insert 22 (orrotary drill bit insert). The cutting insert 22 is made from, forexample, a cemented tungsten carbide that is a mixture of cobalt andtungsten carbide. Other super hard, wear resistant materials such aspolycrystalline diamond, ceramics, or cermet may be used as a supplementand/or substitute. For example chromium carbide-coated metals and othercermets where titanium carbide or vanadium carbide is added to tungstencarbide may be candidates for inserts materials in accordance to aspectsof the invention. Alternate ceramics for such applications includealuminum-based, silicon based, zirconium-based and glass varieties.Still other insert materials alternatives include cubic refractory,transition metal carbides or any other known or subsequently developedmaterial(s) harder than the base material. Also coatings of the insertssuch as PVD or CVD coatings can be used.

Cutting insert 22 has a cutting insert body, generally designated as 24,that has a top surface generally designated as 26, a bottom surfacegenerally designated as 28, and opposite end surfaces generallydesignated as 32 and 34. The cutting insert body 24 is structured andarranged into two opposite symmetric connected portions, i.e. a pair ofsymmetrical halves, which are symmetric about the central axis A-A. Onesymmetric portion includes a leading face 40 and a cutting edge 50formed between the leading face 40 and the top surface 26. In oneaspect, the top surface 26 includes a primary relief surface 44. Inanother aspect, the top surface 26 also includes a secondary reliefsurface 46 wherein the primary relief surface 44 and the secondaryrelief surface 46 are contiguous and non-coplanar. It will beappreciated that each symmetric portion is generally the same and onlyone symmetric portion will be described in detail herein.

The rotary drill bit or roof drill bit assembly 10 also includes an edgeprotector, generally designated as 60, configured to be received in thetransverse slot 18 of the drill bit body 12. The edge protector 60includes a first side 62 having a first bottom edge 64 and a first topedge 66. The edge protector 60 also includes a second side 68 generallyopposed to and/or parallel to the first side 60. The second side 68includes a second bottom edge 70 and a second top edge 72. The edgeprotector 60 also includes a bottom portion 74 adjoining or connectingthe first bottom edge 64 of the first side 62 and the second bottom edge70 of the second side 68.

In accordance with an aspect of the invention, the cutting insert 22 isconfigured to be received in the edge protector 60 such that the cuttingedge 50 is recessed below one of the first top edge 66 of the first side62 or the second top edge 72 of the second side 68. As shown, forexample, in FIG. 4, the cutting edge 50 is recessed below the first topedge 66 of the first side 62. In one aspect, the cutting edge 50 isrecessed below a portion of the first top edge 66 that is generallyparallel to the cutting edge 50 (see, for example, FIG. 4). The firsttop edge 66 (and the second top edge 72) may have various portions thatare not coplanar with one or more of these portions providing theprotection for the cutting edge 50 (and the cutting edge 51). In anotheraspect, the cutting edge 50 is recessed below the first top edge 66 adistance D of about 0.001 inches to about 0.050 inches.

Advantageously, the described and illustrated configuration of thecutting edge 50 with respect to the first top edge 66 of the first side62 provides for the first top edge 66 to protect the cutting edge 50 toprevent, for example, chipping or other damage to the cutting edge 50prior to being used, e.g. during shipping, while installing the hardcutting insert 22, and/or prior to the operation of the roof drill bit10 containing the hard cutting insert 22.

It will be appreciated that the other symmetric portion of the cuttinginsert 22 can include a second cutting edge 51 (see FIG. 1) that isconfigured with respect to the second top edge 72 of the second side 68generally the same as described herein in regards to the cutting edge 50with respect to the first top edge 66 of the first side 62.

The edge protector 60 is positioned within the transverse slot 18 andthe insert 22 is positioned in the edge protector 60. In one aspect, theedge protector 60 is affixed to the slot 18 of the drill bit body 12. Inanother aspect, the cutting insert 22 is affixed to the edge protector60. The cutting insert 22 and the edge protector 60 may be affixed toeach other first and then affixed to the slot 18, or all may be affixedto one another at generally the same time. They may be affixed asdescribed by, for example, attaching mechanically or otherwise, viabrazing or gluing using conventional compositions and techniques knownto those skilled in the art. To assist in, for example, affixing thesecomponents by brazing, the first side 62, second side 68 and/or thebottom portion 74 can include a plurality of perforations 76 formedtherein. The perforations can be of various shapes and sizes and aid inallowing the braze material to flow efficiently in relation to thecutting insert 22, the edge protector 60 and the slot 18 to provide fora better attachment of these components to each other.

In another aspect of the invention, the edge protector 60 is formed of amaterial having a hardness value that is less than a hardness value ofthe cutting insert 22. As described, the cutting insert is made of arelatively hard material such as, for example, cemented tungstencarbide. The edge protector 60 is made with a material such as, forexample, copper, steel, aluminum, brass, triclad, or any iron basedmaterial that is less hard in comparison to the cutting insert 22material. Advantageously, by selecting the relative hardness of the edgeprotector 60 and the cutting insert 22 as described, the edge protector60 will provide the desired shielding or protection for the cuttingedges 50 and 51 while allowing for the roof drill bit 10 to be putdirectly into operation without the need to remove the edge protector 60because the edge protector 60 will wear relatively quickly duringoperation of the roof drill bit 10 to expose or unshield the cuttingedges 50 and 51 so that they may perform the desired cutting operation.

In another aspect, the edge protector 60 may also be configured suchthat other parts of the cutting insert 22 are shielded or protected. Forexample, as illustrated in FIG. 4 an end 78 of the edge protector 60 maybe configured to extend beyond the end 32 of the cutting insert 22 suchthat the end 32 is recessed with respect to the end 78 and protect theend 32. In another aspect, the first top edge 66 and the end 78 of theedge protector combine to protect a corner 50 a of the cutting edge 50.

In another aspect, the edge protector 60 also may be in the form of ashim that also provides and includes the edge protection benefits asdescribed herein. In one aspect, the shim helps the flow of braze tofully and uniformly cover the cutting insert 22 and transverse cuttingslot 18. The shim also helps to provide a uniform gap between thecutting insert 22 and the transverse cutting slot 18.

Whereas particular aspects of this invention have been described abovefor purposes of illustration, it will be evident to those skilled in theart that numerous variations of the details of the present invention maybe made without departing from the invention as defined in the appendedclaims.

What is claimed is:
 1. A rotary drill bit for engaging an earth stratamaterial, the rotary drill bit comprising: an elongate drill bit bodyhaving an axial forward end and an axial rearward end, the drill bitbody containing a slot at the forward end; an edge protector received inthe slot of the drill bit body, the edge protector comprising: a firstside having a first bottom edge and a first top edge; a second sideopposed to the first side, the second side having a second bottom edgeand a second top edge; and a bottom portion adjoining the first bottomedge of the first side and the second bottom edge of the second side;and a cutting insert having an elongate insert body rotatable about acentral axis, the elongate insert body having a pair of symmetricalhalves symmetrical about the central axis, each symmetrical halfcomprising: a leading face; a top surface; and a cutting edge formedbetween the leading face and the top surface, wherein the cutting insertis received in the edge protector such that the cutting edge is recessedbelow one of the first top edge of the first side or the second top edgeof the second side.
 2. The rotary drill bit of claim 1, wherein thecutting edge is recessed below one of the first top edge or the secondtop edge a distance of about 0.001 inches to about 0.050 inches.
 3. Therotary drill bit of claim 2, wherein the cutting edge is parallel to oneof the first top edge or the second top edge.
 4. The rotary drill bit ofclaim 1, wherein the first side, the second side and the bottom portioneach include a plurality of perforations formed therein.
 5. The rotarydrill bit of claim 1, wherein the edge protector is formed of a materialhaving a hardness value that is less than a hardness value of thecutting insert.
 6. The rotary drill bit of claim 1, wherein the edgeprotector is formed of at least one of copper, steel, aluminum, brass,triclad, or any iron based material.
 7. The rotary drill bit of claim 1,wherein the edge protector is affixed to the slot of the drill bit body.8. The rotary drill bit of claim 7, wherein the cutting insert isaffixed to the edge protector.
 9. An edge protector assembly for arotary drill bit, the edge protector assembly comprising: a shim havinga first side having a first bottom edge and a first top edge, a secondside having a second bottom edge and a second top edge, and a bottomportion adjoining the first bottom edge of the first side and the secondbottom edge of the second side; and a cutting insert having a leadingface, a top surface, and a cutting edge formed between the leading faceand the top surface, wherein the cutting insert is received in the shimsuch that the cutting edge is recessed below one of the first top edgeof the first side or the second top edge of the second side.
 10. Theedge protector assembly of claim 9, wherein the cutting edge is recessedbelow one of the first top edge or the second top edge a distance ofabout 0.001 inches to about 0.050 inches.
 11. The edge protectorassembly of claim 10, wherein the cutting edge is parallel to one of thefirst top edge or the second top edge.
 12. The edge protector assemblyof claim 9, wherein the first side, second side and bottom portion eachinclude a plurality of perforations formed therein.
 13. The edgeprotector assembly of claim 9, wherein the shim is formed of a materialhaving a hardness value that is less than a hardness value of thecutting insert.
 14. The edge protector assembly of claim 9, wherein theshim is formed of at least one of copper, steel, aluminum, brass,triclad, or any iron based material.
 15. The edge protector assembly ofclaim 9, wherein the cutting insert is affixed to the shim.
 16. An edgeprotector for a roof drill bit cutting insert having at least onecutting edge, the edge protector comprising: a first side having a firstbottom edge and a first top edge; a second side having a second bottomedge and a second top edge; a bottom portion adjoining the first bottomedge of the first side and the second bottom edge of the second side,wherein the first side, the second side and the bottom portion areconfigured for receiving the cutting insert such that the at least onecutting edge is recessed below the first top edge of the first side orrecessed below the second top edge of the second side.
 17. The edgeprotector of claim 16, wherein one of the first top edge or the secondtop edge is parallel to the at least one cutting edge of the cuttinginsert.
 18. The edge protector of claim 16, wherein the first side,second side and bottom portion each include a plurality of perforationsformed therein.
 19. The edge protector of claim 16, wherein the edgeprotector is formed of a material having a hardness value that is lessthan a hardness value of the cutting insert.
 20. The edge protector ofclaim 16, wherein the edge protector is formed of at least one ofcopper, steel, aluminum, brass, triclad, or any iron based material.